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The relationship between the simulated climatic variability modes of the tropical Atlantic
Author(s) -
Servain Jacques,
Wainer Ilana,
Ludos Ayina Hervé,
Roquet Hervé
Publication year - 2000
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/1097-0088(200007)20:9<939::aid-joc511>3.0.co;2-v
Subject(s) - climatology , intertropical convergence zone , thermocline , equator , tropical atlantic , zonal and meridional , mode (computer interface) , sea surface temperature , geology , walker circulation , teleconnection , atlantic equatorial mode , indian ocean dipole , convergence zone , environmental science , latitude , precipitation , atlantic multidecadal oscillation , el niño southern oscillation , geography , meteorology , geodesy , computer science , operating system
Two main modes of climatic variability occur in the tropical Atlantic Ocean at inter‐annual time‐scales: the equatorial mode, similar to the El Niño phenomenon in the Pacific Ocean, and the meridional mode, or dipole‐like mode, with no Pacific counterpart. The Atlantic equatorial mode is characterized by the occurrence of alternating warm and cold episodes at the equator, on the eastern side of the basin. These events are associated with abnormal variations in the zonal equatorial slope of the thermocline. The meridional mode is characterized by an inter‐hemispheric gradient in the sea‐surface temperature (SST). The mean position of the Inter‐tropical Convergence Zone (ITCZ) separates positive and negative SST signals. It was recently shown with observational indices that there is significant correlation between these two climatic modes of variability. This study goes one step further, by using a multi‐year numerical simulation, where an oceanic general circulation model is forced by the 1979–1993 ECMWF reanalysis. Model computed indices representing the two main modes of variability compare well with observations. The two inter‐annual modes of variability are shown to have the same physics as the annual variability does, which is related to the latitudinal displacement of the ITCZ. Furthermore, it is suggested that the ocean dynamics (as opposed to thermodynamic processes) is the principal cause of climate variability in the region. Copyright © 2000 Royal Meteorological Society